Polyethylene (PE) is commonly used in plastic pipes for gas and water supply, where high-density polyethylene (HDPE) is the most common ingredient. When laying PE pipes or fixing ruptured or broken pipes, the PE pipes are typically joined using fusion welding such as butt fusion, electrofusion, or hot iron fusion.
In general, an electrofusion joint fitting comprises tubular openings adapted to receive a pipe to be connected to the fitting. An electrofusion element is arranged in the tubular opening at the inner surface to be adjacent to the outer surface of the pipe, which is inserted into the fitting. Typically, an electrofusion element comprises an electrical heating coil of resistance wire positioned some distance into the fitting. The electrofusion element can be marked by a rib or edge. The coil is connected to contacts for supplying electric current to the electrical heating coil. When the coil is energized, it heats up and causes the plastic materials of the pipe and the fitting adjacent to the electrofusion element to melt and fuse. The thicknesses of the pipe and the fitting are such that the heat only melts the inner surface of the fitting and the outer surface of the pipe.
Joint seals are the weakest points of any piping system. Welded joints of PE pipes are not always successful (i.e., they do not always have a perfect seal) due to welding errors. Welding errors may occur due to faults in cutting the pipes, poor scraping of the pipe, particles or debris in the welding zone, positioner problems, humidity, incorrect welding parameters, etc.
Currently, in PE, HDPE, or polypropylene (“PP”) piping systems, a pressure test is conducted over a number of joints in a given system. These tests are typically conducted during installation (as often required by law) or at periodic intervals after the initial installation. During the test, a section containing a number of joints is closed off for the test. Upon closing all openings and filling the system with liquid (usually water), pressure is introduced. Typically, the test pressure is increased to 1.5 times the operating pressure, where it is held until it can be read and interpreted for leak tightness. HDPE and other polymers that may comprise these systems have a tendency to stretch. This pliability gives these polymers their toughness which is an asset in these fluid supply systems. However, the downside to the pliability is that the pipe sections balloon during the hydrostatic pressure test. That means that, unlike piping systems whose main ingredient may be a metal or an alloy, an additional time component must be added to the pressure-testing of plastic piping systems to account for the period of time it takes the pipe to reach its maximum ballooned state before the system can then be monitored and assessed for leak tightness. In many cases, it takes many hours for PE piping systems to reach a maximum-ballooned state. A typical hydrostatic pressure test could take 24 hours with more complex systems taking longer. Thus, complex, time-consuming logistics for hydrostatic loading and removal of test fluids are necessary and unavoidable in current practices. A simple and less time-consuming way of testing if the joints are successfully welded is desired.
In addition to improved testing devices, systems, and methods, lack of oversight infrastructure in standard pipe joining technology has allowed leaking joints to remain a global problem in piping systems. Water that leaks from piping systems is referred to as “non-revenue water,” i.e., water that leaks out of water supply pipelines before being metered for revenue (also referred to as “NRW”). Infrastructure is needed to monitor and gather data from joints to reduce NRW and create a smart water network (SWN).